Coronary artery bypass graft (CABG) surgery is a widely practised surgical procedure for performing coronary artery revascularization or bypass grafts. This surgical procedure consists of replenishing or augmenting blood flow to a portion of the patient's heart which is being deprived of such flow due to a restriction or blockage in a coronary artery supplying the said portion of the patient's heart. A healthy segment from a blood vessel, such as an artery or a vein converted into an artery, is attached to the patient's vasculature from a point upstream of the coronary artery restriction or blockage to a point downstream thereof, thereby creating the bypass artery and associated bypass blood flow. Since the great majority of CABG surgeries are multi-vessel bypasses, this surgical procedure remains one of the most common and effective treatments for coronary artery disease.
Traditional CABG surgery has been commonly performed through a midline sternotomy incision, where the patient's sternum is incised and the ribcage retracted to obtain access mainly to the patient's heart, the coronary vessels, and other internal thoracic arteries. Intercostal thoracotomy approaches have also been employed whereby two adjacent ribs are spread apart, at times even removing a length of rib to improve access into the patient's thorax. In both approaches, a surgical retractor is used to spread the patient's skin and bone structure and to maintain an incised opening or surgical window onto the underlying heart and coronary vessels.
CABG surgery has been traditionally performed with the support of a cardio-pulmonary machine, whereby the patient's blood is oxygenated outside the body through extracorporeal circulation (ECC). This allows the surgeon to perform surgical procedures on a near perfectly still heart while the patient's life support is maintained by cardiopulmonary assistance. During traditional CABG surgery, the surgeon or assistant may manually or otherwise manipulate the arrested heart into a position and orientation that yields the best access to the target artery requiring the bypass graft. The great majority of CABG surgeries (approximately 70%) are triple vessel bypass surgeries; that is, at least one bypass graft is performed on each of the anterior, inferior and posterior artery beds of the patient's heart.
Recently, in an aim to render CABG surgery less invasive to the patient, beating heart CABG surgery is being developed whereby ECC, one of the most invasive aspects of cardiac surgery, is eliminated and coronary artery revascularization is performed directly on the beating heart. One of the challenges in performing beating heart CABG surgery lies in positioning and orienting the beating heart in order to obtain access to the inferior and posterior artery beds, while aiming to minimize physiologically undesirable effects such as hemodynamic instability, arrhythmia, or a precipitous drop in arterial pressure, any of which may occur as a result of such beating heart manipulation. Furthermore, a surgical device which enables manipulation of the beating heart or which restrains its movement or positioning may impose loads and constraints on the beating heart. This may impede the normal beating function of the heart and induce the onset of the physiologically undesirable effects described above. In traditional CABG surgery, the heart is arrested and therefore heart manipulations are well tolerated.
During CABG surgery or beating heart CABG surgery, the pericardium, namely the substantially thin membranous tissue forming a sac in which the heart and the commencement of the major blood vessels connecting with the heart are contained, is generally incised and unraveled to expose at least a portion of the heart surface which is to receive the bypass graft. The pericardium tissue, unlike the heart, is not beating and it may be separated from the heart surface except in certain locations where it is anatomically attached to the heart. Thus, it is surgically possible in CABG surgery to position and orient the heart through retraction, positioning and loading of the pericardium tissue to obtain access to the inferior and posterior coronary artery beds. In beating heart CABG, heart manipulations achieved through retraction of the pericardium tissue tends to reduce the likelihood of inducing trauma to the beating heart and tends to minimize the physiologically undesirable effects mentioned above, since direct contact with the beating heart is avoided. One such beating heart manipulation consists of “verticalizing” the heart in order to gain access to the posterior artery bed. In this maneuver, the pericardium is engaged close to the base of the heart, preferably 1.5 inches from pericardial reflection, and the apex of the heart is rotated outward from retracted chest cavity through the tensile loads applied to the engaged pericardium. The longitudinal axis of the beating heart thereby assumes a substantially vertical orientation.
The desired position and orientation of a beating heart may be maintained, at least in part, by maintaining retraction loads applied to the pericardium tissue and securing the surgical apparatus that applies the tensile load to pericardium tissue. During CABG surgery, a deployed surgical retractor provides a suitable stable platform for the securement of the pericardium retraction loads. The pericardium tissue may be engaged by a variety of methods. Sutures such as traction or stay sutures have been generally employed in cardiac surgery to retract tissue during a surgical intervention. Traditionally sutures consist of tissue piercing member such as a relatively sharp needle and a length of wire-like filament such as a suture line integrally attached to the blunt end of said needle. Pericardium retraction may be achieved through the application of pericardial traction sutures whereby the needle pierces the pericardium tissue, threading a certain length of suture line through the pierced pericardium tissue, and pulling simultaneously on both the resulting lengths of suture line; that is, the length between the pierced tissue and the free end of the suture line, and the length between the pierced tissue and the needle-bearing end of the suture line, to displace the pericardium tissue and consequently the beating heart anatomically attached to the pericardium.
In order to “verticalize” a beating with pericardial traction sutures, a number of such sutures must be inserted through and engaged with the pericardium tissue preferably along its pericardial reflection in order to get the desired lifting of the heart apex and consequently the best exposure to the posterior coronary bed. For example, one traction suture may be placed between the superior and inferior pulmonary vein, a second one below the inferior pulmonary vein, a third one midway between the apex of the heart and the inferior pulmonary vein, and a fourth one towards the diaphragmatic face near the inferior vena cava. Pericardium retraction loads are subsequently applied to each of these traction sutures independently. The resulting lengths of suture line must then be secured to a stable surgical platform such as the sternum retractor to maintain the desired retraction load on the pericardium tissue.
During the placement of these pericardial traction sutures deep within the patient's thorax and close to the base of the beating heart, the surgeon's view of the body tissue contained beyond the unraveled pericardium tissue is hindered. Consequently, because of this blind installation, the risk of unintentionally puncturing other underlying body tissue with the tissue piercing needle may lead to operative or postoperative complications, especially when a number of such sutures is required. For instance, an inadvertent puncture of the pleura and lungs may lead to a pneumothorax injury if undetected. The placement of deep pericardial traction sutures may therefore be challenging.
Pericardial traction sutures may be characterized by additional drawbacks. For example the placement of such sutures may be time consuming, since securing of the pericardium retraction load through the manual tying of the suture line lengths is often a multiple step threading and knotting procedure. As well, the placement of pericardial traction sutures may in some instances be cumbersome due to poor access to the deeper portions of pericardial tissue and due to the number of traction sutures required to achieve beating heart “verticalization”. Lastly, these sutures may not be conducive to permitting easy readjustment of the magnitude of the desired tensile load on the pericardium tissue, or of the direction of said load relative to the pericardium tissue. Typically readjustments of this type may require a surgeon to untie and retie suture line lengths or to cut the existing suture line having the undesired retraction load and replace it with a new suture that must repierce the pericardium tissue and again be secured.
Generally, adjustment of the desired tensile load on the pericardium tissue by cutting an existing suture line and repiercing a new suture line is not desirable. First, the process of placing a pericardial traction suture requires considerable manual dexterity, at times requiring the help of an assistant. The process is therefore tedious and time consuming. Second, a repiercing of the pericardium tissue with a subsequent traction suture tends to increase the likelihood of inducing tissue trauma or tissue tearing which may have to be surgically repaired.
Based on the foregoing, it would be advantageous to provide a means for pericardium retraction which is less invasive to the pericardium tissue and underlying coronary tissue, and which is not compromised by a surgeon's lack of vision behind the pericardium tissue. Since the pericardium is a relatively thin, membranous tissue which is incised and unraveled to expose the underlying heart surface prior to performing cardiac surgery, it would be advantageous to have the pericardium tissue engaged by a negative pressure suction force. It would be a further advantage to have the pericardium contacting perimeter of the negative pressure suction device constructed from a substantially flexible material which conforms to variations in anatomy, and which deflects to form a substantial seal when placed in contact with the pericardium and activated by a negative pressure suction force.
Subsequent to securing the desired position and orientation of the beating heart through retraction of the pericardium tissue, coronary artery revascularization may be achieved by locally immobilizing a small portion of the beating heart around the target artery requiring the bypass graft through a variety of ways. One such method consists of immobilizing the portion of beating heart around the target artery through the application of a mechanical compression by virtue of a coronary stabilizer. The remaining portions of the heart continue to beat while the target artery site is immobilized during the bypass graft procedure. One such surgical apparatus for achieving this method of mechanical immobilization has been described in copending Canadian patent application Serial No. 2,216,893 filed on Sep. 30, 1997 in the names of Cartier and Paolitto and entitled “Sternum Retractor for Performing Bypass Surgery on a Beating Heart”. Alternatively, a negative pressure suction has also been used in beating heart CABG to locally immobilize a portion of the beating heart surface in the vicinity of the target artery requiring the bypass graft. An associated device which applies the suction force to the beating heart surface is subsequently secured relative to a stable platform. In this case, the suction port or the structural members of the associated device that applies the negative pressure force must be substantially rigid since the primary purpose of the device is to attempt to immobilize and render motionless that portion of heart tissue it engages in order to create a stable surgical field, while the rest of the heart continues to beat.
U.S. Pat. No. 5,727,569 issued to Benetti et al. on Mar. 17, 1998 and entitled “Surgical Devices for Imposing a Negative Pressure to Fix the Position of Cardiac Tissue during Surgery”, describes a surgical device for imposing a negative pressure directly on a portion of the outer surface of the beating heart. The Benetti device is applied proximate to or surrounding the portion of the outer surface of the beating heart at which a surgical intervention is to occur. By applying negative pressure by means of the Benetti device, the motion of the outer surface of the beating heart is restricted at the particular area where the surgeon is working. The Benetti reference therefore relates to alleviating the problem of performing extremely delicate surgical procedures, like bypass grafting, during which contractions of the beating heart cause the target artery surface of the heart to move continuously. Benetti et al. teach a method of locally and directly immobilizing the target artery location during a surgical intervention intended to occur within the immobilized region.
In contrast to the teachings of the prior art, the present invention herein described relates to surgical manipulation of the pericardium, which is the substantially conical membranous sac in which the heart and the commencement of the major vessels are contained. The Benetti reference does not teach or suggest the positioning and orienting of the entire beating heart as a whole, nor is there any teaching or suggestion therein of retraction of the pericardium to achieve surgical access in an area of the beating heart away from where pericardium retraction device is deployed. Rather, Benetti et al. apply suction around or close to the portion of beating heart tissue proximal to the area where the surgical intervention is to be performed. More specifically, the teachings of Benetti et al. result in immobilization of the pulsating effects of a portion of the exterior surface of the beating heart through negative force application at the target artery site. It would be advantageous to be able to position the beating heart through the deployment of the device in a location remote to the desired site of surgical intervention to tend to facilitate the access and approach of surgical instruments, and to tend to improve the ergonomics of the grafting site and direct visibility thereto. Unlike the teachings of the Benetti reference, which results in the application of suction directly on the beating heart, it would instead be advantageous to apply this suction indirectly on a benign, non-beating part of coronary organ tissue. This will tend to not impede, restrain or restrict the function of the beating heart.
Benetti et al. describe a device with multiple suction ports attached through a negative pressure manifold. In the teachings of Benetti, it is suggested to provide a device having suction ports which share a common negative pressure manifold. However, in such a suggested device, if one suction port is not in contact with underlying tissue to form a seal, then the entire system will tend to be rendered ineffective, at least in part, by the leakage through said port. It would be advantageous to introduce a feature which cuts off flow through non-sealing suction ports with cardiac tissue, thereby tending to maintain effective the entire set-up even if only a portion of the suction ports are properly sealing with the said tissue. Alternatively, Benetti et al. teach that each suction port can have it own independent supply line, which would circumvent this problem through a more complex, cumbersome, and part-intensive set-up. The new invention described herein introduces an embodiment thereof which allows the surgical apparatus, namely the pericardium retraction device, to function with at least a portion of the suction ports in contact with the coronary organ tissue. This embodiment can be applied to other surgical apparatus engaging coronary organ tissue through a negative pressure suction force.
The Benetti reference describes either fixing the suction port device to a rigid support during the procedure, or having the suction port device as a part of a hand-held instrument with a handle structure connected thereto and adapted to being grasped by a human hand. In contrast to the teachings and suggestions of the Benetti reference, it may be advantageous to attach a suction port device to an intermediate positioning means prior to fixturing the complement to a stable surgical platform such as a sternum retractor, in order to achieve flexibility in the surgical set-up to attempt to cater said surgical set-up to distinct patient anatomies.
According to the Benetti teachings, the negative pressure suction is the only input means for activating the device to engage the underlying beating heart tissue. If the suction is lost, the loss will lead to the surgical work-site of the beating heart no longer immobilized and resulting instability from pulsating effects. If other instruments are in contact with the heart at this time, it may also lead to risk of trauma or injury.
In the pericardium retraction device according to the present invention, it would be advantageous to have a design feature in the tissue-engaging member that is activated by the negative pressure suction therein, whereby said design feature comes into contact with a portion of the engaged pericardium tissue and is capable of transmitting a mechanical force to the pericardium tissue being retracted. It would be a further advantage if this said mechanical force remains as a back-up feature in the eventuality that the suction force is interrupted or lost. The embodiment of the invention described herein can be applied to all other surgical apparatus engaging coronary organ tissue.
In “verticalizing” the beating heart through retraction of pericardium tissue, it may be advantageous in some instances to incorporate in the pericardium retraction device a bracing member which engages on the apex of the “verticalized” beating heart, and thereby tends to facilitate in-process re-adjustments of the position and orientation of the entire beating heart by the movement of the surgical apparatus comprising the pericardium retraction device together with the apex-bracing member.
In light of the foregoing it would therefore be advantageous to have a device which acts on a portion of the pericardium tissue, in a location remote to the target artery site where the surgical intervention will take place, to aim to achieve the beating heart manipulations in a least invasive, hemodynamically stable manner, wherein the device would not materially interfere with the normal beating function of the heart. It would be a further advantage if this device would act in an area remote to where the surgical intervention is to occur, thereby tending to improve the surgeon's direct vision and ergonomics of the surgical work-site.
Although the present invention will focus on cardiac surgery, and more specifically CABG surgery performed directly on a beating heart, the principles and concepts may be applied to other types of surgery or surgical interventions that may benefit from the positioning and orientation of a body organ through the retraction of membrane-like body tissue anatomically attached to the said body organ, and capable of being engaged by a negative pressure suction force.
It is therefore an object of the present invention to provide a retraction device that allows the indirect manipulation of a beating heart as a whole through the application and maintenance of a tensile load on the non-beating pericardium tissue anatomically attached to beating heart, and where said pericardium tissue is engaged by a negative pressure suction force.
It is another object of the present invention to engage the non-beating pericardium tissue without piercing therethrough and thereby tending to minimize risk of inducing trauma or damage to organs or tissue behind or adjacent the pericardium.
It is a further object of the present invention to attempt to facilitate posterior artery grafts on the beating heart through indirect manipulation of the beating heart, such that the undesirable physiological effects associated with direct contact manipulation of the beating heart might be alleviated or avoided.
It is a further object of the present invention to attempt to position and orient a beating heart as a whole without the necessity of directly contacting the pulsating heart surface and without materially impeding or restricting the natural beating function of the heart, thereby promoting a reduction in the likelihood of producing undesirable physiological effects associated with direct contact manipulation of the beating heart.
It is another object of the present invention to attempt to position and orient the beating heart indirectly through a device acting at a remote location away from the target work-site on said beating heart where the surgical intervention is to be performed.
It is an additional object of the present invention to attempt to apply the concepts and principles of the present invention as they relate to beating heart CABG to other suitable types of surgery which may require retraction of membrane-like body tissue engaged through a negative pressure suction force.